As at 22 May 2013, PennyTel's rate for SMS is $AU0.05 per message.
Source is published on github: https://github.com/natumbri/SMS-via-PennyTel
Discussion and help on whirlpool: http://forums.whirlpool.net.au/forum-replies.cfm?t=2092455
This app is unofficial, in the sense that it was not created by PennyTel. As a consequence, while PennyTel has assisted in bringing the app to the market, PennyTel is unlikely to be able to provide user support/assistance for the app. Your best bet for support/assistance is the whirlpool forum link above.
Numbers should be in the E164 format. [country code][phone number] (eg - for Australia - 614xxxxxxxx).
No non-number characters should be included in the telephone number (eg. '(', ')', '-', ' ').
The app is currently configured for Australian users, so that Australian numbers not in the E164 format should also work correctly. If the E164 checkbox is selected, telephone numbers with a leading '0' will automatically be sent with a leading '61' (so 04xxxxxxxx will be sent as 614xxxxxxxx). If you try to send to a telephone number with a leading 0 as part of an international dialing code (eg. 0011xxxxxxxxxxx, 011xxxxxxxxx or similar), the leading 0 will be replaced with a '61' and the message may fail. Avoid this by using the E164 format for international numbers.
Future plans include
- user-specified country code (instead of the default Australian '61')
- better integration with the Android system
- more options for user customization
- better handling of non-E164 numbers.